Small changes made while building and running WikiTrust.

I am in the process of trying to build and use WikiTrust because I am evaluating it for use in some of my own research. I have made several changes to the documentation and build scripts — and some small changes in the code — in order to get the software to build and run on my system. I have also updated the documentation to make it more complete and accurate.

I have only very minimal OCaml skills but I think these changes are either not to the .ml files or are simple enough that I think they should be fine. And the software builds and work now on my system.

Thanks for building WikiTrust and thank *so* much for giving it to the world!